1. Field of the Invention
The present invention relates to an engine with a flywheel generator comprising permanent magnets mounted on the outer circumference of a flywheel and a stator confronting the permanent magnets, for generating electric energy to assist a turbocharger in increasing a boost pressure when the engine rotates at low speed.
2. Description of the Prior Art
Conventional engines, particularly two-cycle engines, are required to be supercharged. Since the exhaust and intake strokes of a two-cycle engine are effected at the same time, the exhaust gases are forced out of a cylinder by intake air introduced into the cylinder, and therefore the intake air has to be forced into the cylinder.
Various devices have been proposed to supply intake air under pressure into the cylinder. One of the proposed devices is a turbocharger having an exhaust turbine rotatable by the energy of exhaust gases, and a compressor rotatable by the exhaust turbine to force air under pressure into the cylinder.
As the two-cycle engine has a power stroke each time the crankshaft makes one revolution, the amount of discharged exhaust gases is larger than that of the four-cycle engine. Thus, the two-cycle engine is suitable for driving a turbocharger.
However, even the two-cycle engine discharges a small amount of exhaust energy when it rotates at low speed, and air cannot effectively be forced into the cylinder with such a small amount of exhaust energy.
To overcome the above drawback, there has been proposed a turbocharger with a rotary electric machine connected to the rotatable shaft of the turbocharger. When the rotational speed of the engine is low, the rotary electric machine is supplied with electric energy to operate as a motor which assists the turbocharger to increase the boost pressure.
However, if the electric energy is supplied from a battery to the rotary electric machine, then the battery must be large in size, weight, and volume.
According to another proposal, a recovery turbine is disposed downstream of the exhaust turbine, and actuates a generator to generate electric energy. When the engine rotates at low speed, however, the above problem cannot be solved since the energy of available exhaust gases is small.